Liquid Crystal Display and Method for Driving Same

1. A liquid crystal display, comprising: a liquid crystal panel having a plurality of pixel units, each pixel unit comprising a pixel electrode and a common electrode, and the pixel units cooperatively displaying pictures frame by frame; a scanning driver configured to provide scanning signals to scan the pixel units; a data driver configured to provide data voltage signals to the pixel electrodes of the pixel units; and a common voltage driver configured to provide a common voltage signal to the common electrodes of the pixel units; wherein a dummy cycle period is defined between two sequent normal frame periods, the common voltage signal is an alternating current (AC) voltage signal in each normal frame period, and a polarity of the common voltage signal is fixed in the dummy cycle, and wherein the common voltage signal is one of a positive voltage signal having a variable value and a negative voltage signal having a variable value; the dummy cycle period comprises a first sub-period at the beginning of the dummy cycle period, a second sub-period at the end of the dummy cycle period, and a third sub-period between the first and second sub-periods, a value of the common voltage signal in the first sub-period is substantially the same as that in the second sub-period, and is less than that in the third sub-period.

2. The liquid crystal display of claim 1 , wherein the common voltage signal is an AC voltage signal having a positive value and a negative value alternating with each other in the normal frame period, and is a direct current (DC) voltage signal having a predetermined value in a range between the positive value and the negative value of the AC voltage signal.

3. The liquid crystal display of claim 2 , wherein the predetermined value is half of a sum of the positive value and the negative value of the common voltage signal in the normal frame period.

4. The liquid crystal display of claim 2 , wherein the predetermined value is preset as 0 volts.

5. The liquid crystal display of claim 1 , wherein the scanning driver outputs the scanning signals to the pixel units via n rows of scanning lines, and the data driver outputs the data voltage signals to the pixel units via m columns of data lines; during the dummy cycle period, all the scanning lines are applied with a same predetermined square wave signal having a frequency substantially n times of the scanning signals in the normal frame period.

6. The liquid crystal display of claim 5 , wherein the data voltage signals outputted to the pixel units in the dummy cycle period are repeated as that in a previous normal frame period.

7. The liquid crystal display of claim 1 , wherein the dummy cycle period is configured to provide the data driver with a latency time period for preparing data voltage signals corresponding to a subsequent normal frame period.

8. The liquid crystal display of claim 7 , wherein a length of the dummy cycle period is relevant to a resolution of the liquid crystal panel.

9. The liquid crystal display of claim 7 , wherein a length of the dummy cycle period is preset as a variable value.

10. A liquid crystal display, comprising: a liquid crystal panel having a plurality of pixel units, each pixel unit comprising a pixel electrode and a common electrode, and the pixel units cooperatively displaying pictures frame by frame; a scanning driver configured to provide scanning signals to scan the pixel units; a data driver configured to provide data voltage signals to the pixel electrode of the pixel units; and a common voltage driver configured provide a common voltage signal to the common electrodes of the pixel units; wherein a dummy cycle period is defined between two sequent normal frame periods, the common voltage signal is an alternating current (AC) voltage signal in both the normal frame period and the dummy cycle period, a frequency of the common voltage signal in the dummy cycle period is less than that of the common voltage signal in the normal frame period, and wherein the common voltage signal is one of a positive voltage signal having a variable value and a negative voltage signal having a variable value; the dummy cycle period comprises a first sub-period at the beginning of the dummy cycle period, a second sub-period at the end of the dummy cycle period, and a third sub-period between the first and second sub-periods, a value of the common voltage signal in the first sub-period is substantially the same as that in the second sub-period, and is less than that in the third sub-period.

11. The liquid crystal display of claim 10 , wherein a frequency of the common voltage signal in the dummy cycle period is substantially half of that of the common voltage signal in the normal frame period.

12. The liquid crystal display of claim 11 , wherein the scanning driver outputs a same predetermined square wave signal to all the pixel units during the dummy cycle period, the predetermined square wave signal has a frequency substantially n times of the scanning signals in the normal frame period.

13. The liquid crystal display of claim 12 , wherein the data voltage signals outputted to the pixel units in the dummy cycle period are repeated as that in a previous normal frame period.

14. A method for driving a liquid crystal display, comprising: in a normal frame period, providing a plurality of scanning signal to activate pixel units, and providing data voltage signals and a first common voltage signal to the activated pixel units, the first common voltage signal is an alternating current (AC) voltage signal; entering a dummy cycle period when the normal frame period ends, and providing a second common voltage signal to the pixel units in the dummy cycle period so as to replace the first common voltage signal, the second common voltage signal is a direct current (DC) voltage signal; and entering a subsequent normal frame period when the dummy cycle period ends, and re-providing the first common voltage signal to the pixel units in the subsequent normal frame period so as to replace the second common voltage signal wherein the second common voltage signal is one of a positive voltage signal having a variable value and a negative voltage signal having a variable value; the dummy cycle period comprises a first sub-period at the beginning of the dummy cycle period, a second sub-period at the end of the dummy cycle period, and a third sub-period between the first and second sub-periods, a value of the second common voltage signal in the first sub-period is substantially the same as that in the second sub-period, and is less than that in the third sub-period.

15. The method of claim 14 , wherein the first common voltage is an AC voltage signal having a positive value and a negative value alternate with each other in the normal frame period, and the second common voltage is a DC voltage signal having a predetermined value in a range between the positive value and the negative value of the AC voltage signal.

16. The method of claim 15 , wherein the predetermined value is half of a sum of the positive value and the negative value of the common voltage signal in the normal frame period.

17. The method of claim 14 , further comprising: providing, during the dummy cycle period, a same predetermined square wave signal to all the pixel units as the scanning signals, wherein the predetermined square wave signal has a frequency substantially n times of the scanning signals in the normal frame period.

18. The method of claim 14 , further comprising: repeating, during the dummy cycle period, to output the data voltage signals of the normal frame period to the pixel units.